Electrical service providers such as electrical utilities employ electricity meters to monitor energy consumption by customers (or other entities). Electricity meters track the amount of energy consumed by a load (e.g. the customer), typically measured in kilowatt-hours (“kwh”), at each customer's facility. The service provider uses the consumption information primarily for billing, but also for resource allocation planning and other purposes.
Electrical power is transmitted and delivered to load in many forms. For example, electrical power may be delivered as polyphase wye-connected or delta-connected power or as single phase power. Such various forms are known as service types. Different standard electricity meter types, known as meter forms, are used to measure the power consumption for the various service types. The commonly used meter forms in the United States include those designated as 2S, 3S, 5S, 45S, 6S, 36S, 9S, 16S, 12S and 25S meter forms, which are well known in the art.
Electrical service providers have historically billed for electrical service in arrears, using information stored within the electricity meter to determine the amount of each invoice. In a typical operation, the electricity meter stores a value representative of the amount of energy consumed in a mechanical or electronic accumulation register. From time to time, the electrical service provider obtains the value of the register and bills the customer accordingly. For example, a meter reader employed by the service provider may, each month, physically read the register value off of a meter display. The service provider then employs the obtained register value to determine the amount of electricity consumed over the month and bills the customer for the determined amount.
Historically, electricity meters employed electromechanical means, including rotating disks and mechanical counters, to detect and register electricity consumption. While such electromechanical meters are still common, meters increasing employ digital processing circuitry instead of the rotating disk and mechanical counters. In such meters, sensors within the meter detect the voltage and current that is delivered to the load. Circuitry within the meter converts the sensed voltage and current into digital values. Processing circuitry then employs digital signal processing to calculate consumed energy, among other things, from the digital values. Electronic meters provide greater flexibility in the types of energy consumption information that they can calculate, track, and store. Electronic meters can also facilitate remote meter reading by including a communication means such as radio communication circuits.
One of the few drawbacks of electronic meters is that the metrology and processing circuits require an electronic power supply. While electrical power is readily available in an electricity meter, issues can arise in the event of an electrical service interruption. During electrical service interruption, the electronic power supply cannot operate and is unable to bias the internal circuits. As a consequence, stored data can be lost during a power outage. To avoid such losses, it is known to employ temporary power from a battery or large capacitor to store critical meter data to non-volatile memory within the meter in the event of an external power interruption. The capacitor or battery provides temporary power for the meter to gracefully power down when the external utility power is lost.
Another issue relating to electrical service interruptions arises from a relatively recent feature in metering known as “last gasp” transmissions. With the increasing use of RF communications in meters, utilities find it advantageous to receive a radio transmission from meters when they detect a power service interruption. This transmission ideally occurs before the meter loses all power. The utilities can use such transmissions from several meters in an affected area to help locate the source of the service issue. However, the communication devices inside the electricity meter (including mechanical meters that employ communication circuits) require some form of energy storage to allow for a “last gasp” transmission feature in the event of a power outage. It is common to implement a storage device such as an electrolytic capacitor to provide the necessary energy in the event of a power outage.
A further feature sometimes employed in electricity meters is a switch that disconnects and reconnects the customer load to the electrical service upon receiving a command to operate. Such switches are sometimes referred to as service switches. Service switches commonly use a DC solenoid mechanism or a DC gear motor mechanism to effect a switching operation. To provide the necessary energy for a switching operation the power supply needs to be designed with enough capacity to source the necessary energy to operate the switch. Alternately a smaller power supply is sometimes used in conjunction with an energy storage device, such as an electrolytic capacitor, where the energy stored in the capacitor is used to operate the switch. In the case of a smaller power supply, the energy storage capacitor is first “charged” over a period of time, such as several seconds, before a switching operation is performed.
One issue with meters is the additional size and components required to facilitate power fail operations and service switch operations. There is a need therefore, for a metering arrangement that employs power fail operations and service switch operations with reduced component count and/or size.